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Mastrandrea CJ, Hedge ET, Robertson AD, Heckman GA, Ho J, Granados Unger F, Hughson RL. High-intensity exercise does not protect against orthostatic intolerance following bedrest in 55- to 65-yr-old men and women. Am J Physiol Regul Integr Comp Physiol 2023; 325:R107-R119. [PMID: 37184226 DOI: 10.1152/ajpregu.00315.2022] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2022] [Revised: 04/20/2023] [Accepted: 05/09/2023] [Indexed: 05/16/2023]
Abstract
Prolonged bedrest provokes orthostatic hypotension and intolerance of upright posture. Limited data are available on the cardiovascular responses of older adults to head-up tilt following bedrest, with no studies examining the potential benefits of exercise to mitigate intolerance in this age group. This randomized controlled trial of head-down bedrest (HDBR) in 55- to 65-yr-old men and women investigated if exercise could avert post-HDBR orthostatic intolerance. Twenty-two healthy older adults (11 female) underwent a strict 14-day HDBR and were assigned to either an exercise (EX) or control (CON) group. The exercise intervention included high-intensity, aerobic, and resistance exercises. Head-up tilt-testing to a maximum of 15 minutes was performed at baseline (Pre-Bedrest) and immediately after HDBR (R1), as well as 6 days (R6) and 4 weeks (R4wk) later. At Pre-Bedrest, three participants did not complete the full 15 minutes of tilt. At R1, 18 did not finish, with no difference in tilt end time between CON (422 ± 287 s) and EX (409 ± 346 s). No differences between CON and EX were observed at R6 or R4wk. At R1, just 1 participant self-terminated the test with symptoms, while 12 others reported symptoms only after physiological test termination criteria were reached. Finishers on R1 protected arterial pressure with higher total peripheral resistance relative to Pre-Bedrest. Cerebral blood velocity decreased linearly with reductions in arterial pressure, end-tidal CO2, and cardiac output. High-intensity interval exercise did not benefit post-HDBR orthostatic tolerance in older adults. Multiple factors were associated with the reduction in cerebral blood velocity leading to intolerance.
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Affiliation(s)
| | - Eric T Hedge
- Schlegel-UW Research Institute for Aging, Waterloo, Ontario, Canada
- Department of Kinesiology and Health Studies, University of Waterloo, Waterloo, Ontario, Canada
| | - Andrew D Robertson
- Schlegel-UW Research Institute for Aging, Waterloo, Ontario, Canada
- Department of Kinesiology and Health Studies, University of Waterloo, Waterloo, Ontario, Canada
| | - George A Heckman
- Schlegel-UW Research Institute for Aging, Waterloo, Ontario, Canada
| | - Joanne Ho
- Schlegel-UW Research Institute for Aging, Waterloo, Ontario, Canada
| | - Federico Granados Unger
- Department of Kinesiology and Health Studies, University of Waterloo, Waterloo, Ontario, Canada
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2
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Hedge ET, Patterson CA, Mastrandrea CJ, Sonjak V, Hajj-Boutros G, Faust A, Morais JA, Hughson RL. Implementation of exercise countermeasures during spaceflight and microgravity analogue studies: Developing countermeasure protocols for bedrest in older adults (BROA). Front Physiol 2022; 13:928313. [PMID: 36017336 PMCID: PMC9395735 DOI: 10.3389/fphys.2022.928313] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2022] [Accepted: 06/27/2022] [Indexed: 12/18/2022] Open
Abstract
Significant progress has been made in the development of countermeasures to attenuate the negative consequences of prolonged exposure to microgravity on astronauts’ bodies. Deconditioning of several organ systems during flight includes losses to cardiorespiratory fitness, muscle mass, bone density and strength. Similar deconditioning also occurs during prolonged bedrest; any protracted time immobile or inactive, especially for unwell older adults (e.g., confined to hospital beds), can lead to similar detrimental health consequences. Due to limitations in physiological research in space, the six-degree head-down tilt bedrest protocol was developed as ground-based analogue to spaceflight. A variety of exercise countermeasures have been tested as interventions to limit detrimental changes and physiological deconditioning of the musculoskeletal and cardiovascular systems. The Canadian Institutes of Health Research and the Canadian Space Agency recently provided funding for research focused on Understanding the Health Impact of Inactivity to study the efficacy of exercise countermeasures in a 14-day randomized clinical trial of six-degree head-down tilt bedrest study in older adults aged 55–65 years old (BROA). Here we will describe the development of a multi-modality countermeasure protocol for the BROA campaign that includes upper- and lower-body resistance exercise and head-down tilt cycle ergometry (high-intensity interval and continuous aerobic exercise training). We provide reasoning for the choice of these modalities following review of the latest available information on exercise as a countermeasure for inactivity and spaceflight-related deconditioning. In summary, this paper sets out to review up-to-date exercise countermeasure research from spaceflight and head-down bedrest studies, whilst providing support for the proposed research countermeasure protocols developed for the bedrest study in older adults.
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Affiliation(s)
- Eric T. Hedge
- Schlegel-University of Waterloo Research Institute for Aging, Waterloo, ON, Canada
- Department of Kinesiology and Health Sciences, University of Waterloo, Waterloo, ON, Canada
| | | | | | - Vita Sonjak
- Research Institute of McGill University Health Centre, McGill University, Montréal, QC, Canada
| | - Guy Hajj-Boutros
- Research Institute of McGill University Health Centre, McGill University, Montréal, QC, Canada
| | - Andréa Faust
- Research Institute of McGill University Health Centre, McGill University, Montréal, QC, Canada
| | - José A. Morais
- Research Institute of McGill University Health Centre, McGill University, Montréal, QC, Canada
- Division of Geriatric Medicine, McGill University Health Centre, McGill University, Montréal, QC, Canada
| | - Richard L. Hughson
- Schlegel-University of Waterloo Research Institute for Aging, Waterloo, ON, Canada
- *Correspondence: Richard L. Hughson,
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3
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Rodrigues GD, Gurgel JL, da Nobrega ACL, Soares PPDS. Orthostatic intolerance: a handicap of aging or physical deconditioning? Eur J Appl Physiol 2022; 122:2005-2018. [PMID: 35716190 DOI: 10.1007/s00421-022-04978-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2022] [Accepted: 05/27/2022] [Indexed: 11/24/2022]
Abstract
Despite several studies that have been investigated physical inactivity and age-related effects on orthostatic tolerance, impaired hemodynamics and postural balance responses to orthostatic stress are incorrectly attributed to aging or sedentarism alone. The isolated effects from aging and sedentarism should be investigated through comparative studies between senior athletes and age-matched controls, and physical activity assessments on aging follow-up studies. On the other hand, bed rest and space flight studies mimic accelerated physical inactivity or disuse, which is not the same physiological decline provoked by aging alone. Thus, the elementary question is: could orthostatic intolerance be attributed to aging or physical inactivity? The main purpose of this review is to provide an overview of possible mechanisms underlying orthostatic tolerance contrasting the paradigm of aging and/or physical inactivity. The key points of this review are the following: (1) to counterpoint all relevant literature on physiological aspects of orthostatic tolerance; (2) to explore the mechanistic aspects underneath the cerebrovascular, cardiorespiratory, and postural determinants of orthostatic tolerance; and (3) examine non-pharmacological interventions with the potential to counterbalance the physical inactivity and aging effects. To date, the orthostatic intolerance cannot be attributed exclusively with aging since physical inactivity plays an important role in postural balance, neurovascular and cardiorespiratory responses to orthostatic stress. These physiological determinates should be interpreted within an integrative approach of orthostatic tolerance, that considers the interdependence between physiological systems in a closed-loop model. Based on this multisystem approach, acute and chronic countermeasures may combat aging and sedentarism effects on orthostatic tolerance.
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Affiliation(s)
- Gabriel Dias Rodrigues
- Department of Physiology and Pharmacology, Fluminense Federal University, Niterói, Brazil.,Department of Clinical Sciences and Community Health, University of Milan, Milan, Italy.,National Institute for Science & Technology - INCT, (In)activity & Exercise, CNPq-Niterói (RJ), Rio de Janeiro, Brazil
| | - Jonas Lírio Gurgel
- Department of Physical Education and Sports, Fluminense Federal University, Niterói, Brazil
| | - Antonio Claudio Lucas da Nobrega
- Department of Physiology and Pharmacology, Fluminense Federal University, Niterói, Brazil.,National Institute for Science & Technology - INCT, (In)activity & Exercise, CNPq-Niterói (RJ), Rio de Janeiro, Brazil
| | - Pedro Paulo da Silva Soares
- Department of Physiology and Pharmacology, Fluminense Federal University, Niterói, Brazil. .,National Institute for Science & Technology - INCT, (In)activity & Exercise, CNPq-Niterói (RJ), Rio de Janeiro, Brazil.
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4
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Roberts DR, Collins HR, Lee JK, Taylor JA, Turner M, Zaharchuk G, Wintermark M, Antonucci MU, Mulder ER, Gerlach DA, Asemani D, McGregor HR, Seidler RD. Altered cerebral perfusion in response to chronic mild hypercapnia and head-down tilt Bed rest as an analog for Spaceflight. Neuroradiology 2021; 63:1271-1281. [PMID: 33587162 DOI: 10.1007/s00234-021-02660-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2020] [Accepted: 01/26/2021] [Indexed: 01/01/2023]
Abstract
PURPOSE Following prolonged stays on the International Space Station (ISS), some astronauts exhibit visual acuity changes, ophthalmological findings, and mildly elevated intracranial pressures as part of a novel process called spaceflight-associated neuro-ocular syndrome (SANS). To determine the pathophysiology of SANS, NASA conducted a multi-investigator study in which 11 healthy participants underwent head-down tilt bed rest, mimicking microgravity-induced cephalad fluid shifts, combined with elevated ambient CO2 levels similar to those on the ISS (HDT+CO2). As part of that study, we examined the effects of HDT+CO2 on cerebral perfusion. METHODS Using arterial spin labeling, we compared cerebral perfusion before, during, and after HDT+CO2 in participants who developed SANS (n = 5) with those who did not (n = 6). RESULTS All participants demonstrated a decrease in perfusion during HDT+CO2 (mean decrease of 25.1% at HDT7 and 16.2% at HDT29); however, the timing and degree of change varied between the groups. At day 7 of HDT+CO2, the SANS group experienced a greater reduction in perfusion than the non-SANS group (p =.05, 95% CI:-0.19 to 16.11, d=.94, large effect). Conversely, by day 29 of HDT+CO2, the SANS group had significantly higher perfusion (approaching their baseline) than the non-SANS group (p = .04, 95% CI:0.33 to 13.07, d=1.01, large effect). CONCLUSION Compared with baseline and recovery, HDT+CO2 resulted in reduced cerebral perfusion which varied based on SANS status. Further studies are needed to unravel the relative role of HDT vs hypercapnia, to determine if these perfusion changes are clinically relevant, and whether perfusion changes contribute to the development of SANS during spaceflight.
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Affiliation(s)
- Donna R Roberts
- Department of Radiology and Radiological Science, Medical University of South Carolina, Charleston, SC, USA. .,Department of Neuroscience, Medical University of South Carolina, Charleston, SC, USA.
| | - Heather R Collins
- Department of Radiology and Radiological Science, Medical University of South Carolina, Charleston, SC, USA
| | - Jessica K Lee
- German Aerospace Center (DLR, Institute of Aerospace Medicine), Cologne, Germany.,Department of Applied Physiology and Kinesiology, College of Health and Human Performance, University of Florida, Gainesville, FL, USA
| | - James A Taylor
- Department of Radiology and Radiological Science, Medical University of South Carolina, Charleston, SC, USA
| | - Matthew Turner
- Department of Radiology and Radiological Science, Medical University of South Carolina, Charleston, SC, USA
| | - Greg Zaharchuk
- Department of Radiology, Division of Neuroradiology, Stanford University, Stanford, CA, USA
| | - Max Wintermark
- Department of Radiology, Division of Neuroradiology, Stanford University, Stanford, CA, USA
| | - Michael U Antonucci
- Department of Radiology and Radiological Science, Medical University of South Carolina, Charleston, SC, USA
| | - Edwin R Mulder
- German Aerospace Center (DLR, Institute of Aerospace Medicine), Cologne, Germany
| | - Darius A Gerlach
- German Aerospace Center (DLR, Institute of Aerospace Medicine), Cologne, Germany
| | - Davud Asemani
- Department of Radiology and Radiological Science, Medical University of South Carolina, Charleston, SC, USA
| | - Heather R McGregor
- Department of Applied Physiology and Kinesiology, College of Health and Human Performance, University of Florida, Gainesville, FL, USA
| | - Rachael D Seidler
- Department of Applied Physiology and Kinesiology, College of Health and Human Performance, University of Florida, Gainesville, FL, USA.,Norman Fixel Institute for Neurological Diseases, College of Health and Human Performance, University of Florida, Gainesville, FL, USA
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5
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Ogoh S, Sato K, Abreu S, Denise P, Normand H. Arterial and venous cerebral blood flow responses to long‐term head‐down bed rest in male volunteers. Exp Physiol 2019; 105:44-52. [DOI: 10.1113/ep088057] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2019] [Accepted: 11/04/2019] [Indexed: 12/17/2022]
Affiliation(s)
- Shigehiko Ogoh
- Department of Biomedical Engineering Toyo University Kawagoe‐Shi Saitama Japan
| | - Kohei Sato
- Tokyo Gakugei University Koganei Tokyo Japan
| | - Steven Abreu
- Normandie Université, Unicaen; Inserm Comete GIP Cyceron Chu Caen France
| | - Pierre Denise
- Normandie Université, Unicaen; Inserm Comete GIP Cyceron Chu Caen France
| | - Hervé Normand
- Normandie Université, Unicaen; Inserm Comete GIP Cyceron Chu Caen France
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6
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Huang M, Brothers RM, Ganio MS, Lucas RAI, Cramer MN, Moralez G, Convertino VA, Crandall CG. Tolerance to a haemorrhagic challenge during heat stress is improved with inspiratory resistance breathing. Exp Physiol 2018; 103:1243-1250. [PMID: 29947436 PMCID: PMC6119106 DOI: 10.1113/ep087102] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2018] [Accepted: 06/22/2018] [Indexed: 02/06/2023]
Abstract
NEW FINDINGS What is the central question of this study? Does inspiratory resistance breathing improve tolerance to simulated haemorrhage in individuals with elevated internal temperatures? What is the main finding and its importance? The main finding of this study is that inspiratory resistance breathing modestly improves tolerance to a simulated progressive haemorrhagic challenge during heat stress. These findings demonstrate a scenario in which exploitation of the respiratory pump can ameliorate serious conditions related to systemic hypotension. ABSTRACT Heat exposure impairs human blood pressure control and markedly reduces tolerance to a simulated haemorrhagic challenge. Inspiratory resistance breathing enhances blood pressure control and improves tolerance during simulated haemorrhage in normothermic individuals. However, it is unknown whether similar improvements occur with this manoeuvre in heat stress conditions. In this study, we tested the hypothesis that inspiratory resistance breathing improves tolerance to simulated haemorrhage in individuals with elevated internal temperatures. On two separate days, eight subjects performed a simulated haemorrhage challenge [lower-body negative pressure (LBNP)] to presyncope after an increase in internal temperature of 1.3 ± 0.1°C. During one trial, subjects breathed through an inspiratory impedance device set at 0 cmH2 O of resistance (Sham), whereas on a subsequent day the device was set at -7 cmH2 O of resistance (ITD). Tolerance was quantified as the cumulative stress index. Subjects were more tolerant to the LBNP challenge during the ITD protocol, as indicated by a > 30% larger cumulative stress index (Sham, 520 ± 306 mmHg min; ITD, 682 ± 324 mmHg min; P < 0.01). These data indicate that inspiratory resistance breathing modestly improves tolerance to a simulated progressive haemorrhagic challenge during heat stress.
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Affiliation(s)
- Mu Huang
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital, Dallas, TX, USA
- Department of Health Care Sciences, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - R Matthew Brothers
- Department of Kinesiology, University of Texas, Arlington, Arlington, TX, USA
| | - Matthew S Ganio
- Department of Health, Human Performance and Recreation, University of Arkansas, Fayetteville, AR, USA
| | - Rebekah A I Lucas
- School of Sport, Exercise & Rehabilitation Sciences, The University of Birmingham, Edgbaston, Birmingham, UK
| | - Matthew N Cramer
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital, Dallas, TX, USA
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Gilbert Moralez
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital, Dallas, TX, USA
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | | | - Craig G Crandall
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital, Dallas, TX, USA
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX, USA
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7
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van Helmond N, Johnson BD, Holbein WW, Petersen‐Jones HG, Harvey RE, Ranadive SM, Barnes JN, Curry TB, Convertino VA, Joyner MJ. Effect of acute hypoxemia on cerebral blood flow velocity control during lower body negative pressure. Physiol Rep 2018; 6:e13594. [PMID: 29464923 PMCID: PMC5820424 DOI: 10.14814/phy2.13594] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2017] [Revised: 01/03/2018] [Accepted: 01/05/2018] [Indexed: 11/24/2022] Open
Abstract
The ability to maintain adequate cerebral blood flow and oxygenation determines tolerance to central hypovolemia. We tested the hypothesis that acute hypoxemia during simulated blood loss in humans would cause impairments in cerebral blood flow control. Ten healthy subjects (32 ± 6 years, BMI 27 ± 2 kg·m-2 ) were exposed to stepwise lower body negative pressure (LBNP, 5 min at 0, -15, -30, and -45 mmHg) during both normoxia and hypoxia (Fi O2 = 0.12-0.15 O2 titrated to an SaO2 of ~85%). Physiological responses during both protocols were expressed as absolute changes from baseline, one subject was excluded from analysis due to presyncope during the first stage of LBNP during hypoxia. LBNP induced greater reductions in mean arterial pressure during hypoxia versus normoxia (MAP, at -45 mmHg: -20 ± 3 vs. -5 ± 3 mmHg, P < 0.01). Despite differences in MAP, middle cerebral artery velocity responses (MCAv) were similar between protocols (P = 0.41) due to increased cerebrovascular conductance index (CVCi) during hypoxia (main effect, P = 0.04). Low frequency MAP (at -45 mmHg: 17 ± 5 vs. 0 ± 5 mmHg2 , P = 0.01) and MCAv (at -45 mmHg: 4 ± 2 vs. -1 ± 1 cm·s-2 , P = 0.04) spectral power density, as well as low frequency MAP-mean MCAv transfer function gain (at -30 mmHg: 0.09 ± 0.06 vs. -0.07 ± 0.06 cm·s-1 ·mmHg-1 , P = 0.04) increased more during hypoxia versus normoxia. Contrary to our hypothesis, these findings support the notion that cerebral blood flow control is not impaired during exposure to acute hypoxia and progressive central hypovolemia despite lower MAP as a result of compensated increases in cerebral conductance and flow variability.
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Affiliation(s)
| | - Blair D. Johnson
- Center for Research and Education in Special EnvironmentsDepartment of Exercise and Nutrition SciencesUniversity at BuffaloBuffaloNew York
| | | | | | - Ronée E. Harvey
- Mayo Clinic School of Medicine and ScienceMayo ClinicRochesterMinnesota
| | | | - Jill N. Barnes
- Department of KinesiologyUniversity of Wisconsin‐MadisonMadisonWisconsin
| | | | - Victor A. Convertino
- US Army Battlefield Health & Trauma Center for Human Integrative PhysiologyFort Sam HoustonTexas
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8
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Ogoh S, Hirasawa A, de Abreu S, Denise P, Normand H. Internal carotid, external carotid and vertebral artery blood flow responses to 3 days of head-out dry immersion. Exp Physiol 2017; 102:1278-1287. [DOI: 10.1113/ep086507] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2017] [Accepted: 07/18/2017] [Indexed: 01/23/2023]
Affiliation(s)
- Shigehiko Ogoh
- Department of Biomedical Engineering; Toyo University; Kawagoe-Shi Saitama Japan
| | - Ai Hirasawa
- Faculty of Health Science, Department of Health and Welfare; Kyorin University; Mitaka-shi Tokyo Japan
| | - Steven de Abreu
- Normandie University, Unicaen; Inserm Comete; Chu Caen France
| | - Pierre Denise
- Normandie University, Unicaen; Inserm Comete; Chu Caen France
| | - Hervé Normand
- Normandie University, Unicaen; Inserm Comete; Chu Caen France
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9
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Xing CY, Tarumi T, Liu J, Zhang Y, Turner M, Riley J, Tinajero CD, Yuan LJ, Zhang R. Distribution of cardiac output to the brain across the adult lifespan. J Cereb Blood Flow Metab 2017; 37:2848-2856. [PMID: 27789785 PMCID: PMC5536794 DOI: 10.1177/0271678x16676826] [Citation(s) in RCA: 78] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/13/2016] [Revised: 09/23/2016] [Accepted: 10/04/2016] [Indexed: 11/16/2022]
Abstract
A widely accepted dogma is that about 15-20% of cardiac output is received by the brain in healthy adults under resting conditions. However, it is unclear if the distribution of cardiac output directed to the brain alters across the adult lifespan and is modulated by sex or other hemodynamic variables. We measured cerebral blood flow/cardiac output ratio index in 139 subjects (88 women, age 21-80 years) using phase-contrast magnetic resonance imaging and echocardiography. Body mass index, cardiac systolic function (eject fraction), central arterial stiffness (carotid-femoral pulse wave velocity), arterial pressure, heart rate, physical fitness (VO2 max), and total brain volume were measured to assess their effects on the cardiac output-cerebral blood flow relationship. Cerebral blood flow/cardiac output ratio index decreased by 1.3% per decade associated with decreases in cerebral blood flow ( P < 0.001), while cardiac output remained unchanged. Women had higher cerebral blood flow, lower cardiac output, and thus higher cerebral blood flow/cardiac output ratio index than men across the adult lifespan. Age, body mass index, carotid-femoral pulse wave velocity, and arterial pressure all had negative correlations with cerebral blood flow and cerebral blood flow/cardiac output ratio index ( P < 0.05). Multivariable analysis adjusted for sex, age showed that only body mass index was negatively associated with cerebral blood flow/cardiac output ratio index (β = -0.33, P < 0.001). These findings demonstrated that cardiac output distributed to the brain has sex differences and decreases across the adult lifespan and is inversely associated with body mass index.
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Affiliation(s)
- Chang-Yang Xing
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, USA
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, USA
- Department of Ultrasound Diagnostics, Tangdu Hospital, Fourth Military Medical University, Xi’an, China
| | - Takashi Tarumi
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, USA
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, USA
| | - Jie Liu
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, USA
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, USA
- Department of Ultrasound Diagnostics, Tangdu Hospital, Fourth Military Medical University, Xi’an, China
| | - Yinan Zhang
- Department of Neurology and Neurotherapeutics, University of Texas Southwestern Medical Center, Dallas, USA
| | - Marcel Turner
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, USA
| | - Jonathan Riley
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, USA
| | - Cynthia Duron Tinajero
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, USA
| | - Li-Jun Yuan
- Department of Ultrasound Diagnostics, Tangdu Hospital, Fourth Military Medical University, Xi’an, China
| | - Rong Zhang
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital Dallas, Dallas, USA
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, USA
- Department of Neurology and Neurotherapeutics, University of Texas Southwestern Medical Center, Dallas, USA
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10
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Kay VL, Sprick JD, Rickards CA. Cerebral oxygenation and regional cerebral perfusion responses with resistance breathing during central hypovolemia. Am J Physiol Regul Integr Comp Physiol 2017; 313:R132-R139. [PMID: 28539354 DOI: 10.1152/ajpregu.00385.2016] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2016] [Revised: 04/21/2017] [Accepted: 05/11/2017] [Indexed: 11/22/2022]
Abstract
Resistance breathing improves tolerance to central hypovolemia induced by lower body negative pressure (LBNP), but this is not related to protection of anterior cerebral blood flow [indexed by mean middle cerebral artery velocity (MCAv)]. We hypothesized that inspiratory resistance breathing improves tolerance to central hypovolemia by maintaining cerebral oxygenation (ScO2), and protecting cerebral blood flow in the posterior cerebral circulation [indexed by posterior cerebral artery velocity (PCAv)]. Eight subjects (4 male/4 female) completed two experimental sessions of a presyncopal-limited LBNP protocol (3 mmHg/min onset rate) with and without (Control) resistance breathing via an impedance threshold device (ITD). ScO2 (via near-infrared spectroscopy), MCAv and PCAv (both via transcranial Doppler ultrasound), and arterial pressure (via finger photoplethysmography) were measured continuously. Hemodynamic responses were analyzed between the Control and ITD condition at baseline (T1) and the time representing 10 s before presyncope in the Control condition (T2). While breathing on the ITD increased LBNP tolerance from 1,506 ± 75 s to 1,704 ± 88 s (P = 0.003), both mean MCAv and mean PCAv were similar between conditions at T2 (P ≥ 0.46), and decreased by the same magnitude with and without ITD breathing (P ≥ 0.53). ScO2 also decreased by ~9% with or without ITD breathing at T2 (P = 0.97), and there were also no differences in deoxygenated (dHb) or oxygenated hemoglobin (HbO2) between conditions at T2 (P ≥ 0.43). There was no evidence that protection of regional cerebral blood velocity (i.e., anterior or posterior cerebral circulation) nor cerebral oxygen extraction played a key role in the determination of tolerance to central hypovolemia with resistance breathing.
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Affiliation(s)
- Victoria L Kay
- Institute for Cardiovascular and Metabolic Diseases, University of North Texas Health Science Center, Fort Worth, Texas
| | - Justin D Sprick
- Institute for Cardiovascular and Metabolic Diseases, University of North Texas Health Science Center, Fort Worth, Texas
| | - Caroline A Rickards
- Institute for Cardiovascular and Metabolic Diseases, University of North Texas Health Science Center, Fort Worth, Texas
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11
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Kay VL, Rickards CA. The role of cerebral oxygenation and regional cerebral blood flow on tolerance to central hypovolemia. Am J Physiol Regul Integr Comp Physiol 2016; 310:R375-83. [DOI: 10.1152/ajpregu.00367.2015] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2015] [Accepted: 12/14/2015] [Indexed: 11/22/2022]
Abstract
Tolerance to central hypovolemia is highly variable, and accumulating evidence suggests that protection of anterior cerebral blood flow (CBF) is not an underlying mechanism. We hypothesized that individuals with high tolerance to central hypovolemia would exhibit protection of cerebral oxygenation (ScO2), and prolonged preservation of CBF in the posterior vs. anterior cerebral circulation. Eighteen subjects (7 male/11 female) completed a presyncope-limited lower body negative pressure (LBNP) protocol (3 mmHg/min onset rate). ScO2 (via near-infrared spectroscopy), middle cerebral artery velocity (MCAv), posterior cerebral artery velocity (PCAv) (both via transcranial Doppler ultrasound), and arterial pressure (via finger photoplethysmography) were measured continuously. Subjects who completed ≥70 mmHg LBNP were classified as high tolerant (HT; n = 7) and low tolerant (LT; n = 11) if they completed ≤60 mmHg LBNP. The minimum difference in LBNP tolerance between groups was 193 s (LT = 1,243 ± 185 s vs. HT = 1,996 ± 212 s; P < 0.001; Cohen's d = 3.8). Despite similar reductions in mean MCAv in both groups, ScO2 decreased in LT subjects from −15 mmHg LBNP ( P = 0.002; Cohen's d=1.8), but was maintained at baseline values until −75 mmHg LBNP in HT subjects ( P < 0.001; Cohen's d = 2.2); ScO2 was lower at −30 and −45 mmHg LBNP in LT subjects ( P ≤ 0.02; Cohen's d ≥ 1.1). Similarly, mean PCAv decreased below baseline from −30 mmHg LBNP in LT subjects ( P = 0.004; Cohen's d = 1.0), but remained unchanged from baseline in HT subjects until −75 mmHg ( P = 0.006; Cohen's d = 2.0); PCAv was lower at −30 and −45 mmHg LBNP in LT subjects ( P ≤ 0.01; Cohen's d ≥ 0.94). Individuals with higher tolerance to central hypovolemia exhibit prolonged preservation of CBF in the posterior cerebral circulation and sustained cerebral tissue oxygenation, both associated with a delay in the onset of presyncope.
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Affiliation(s)
- Victoria L. Kay
- Institute for Cardiovascular and Metabolic Diseases, University of North Texas Health Science Center, Fort Worth, Texas
| | - Caroline A. Rickards
- Institute for Cardiovascular and Metabolic Diseases, University of North Texas Health Science Center, Fort Worth, Texas
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Rickards CA, Johnson BD, Harvey RE, Convertino VA, Joyner MJ, Barnes JN. Cerebral blood velocity regulation during progressive blood loss compared with lower body negative pressure in humans. J Appl Physiol (1985) 2015; 119:677-85. [PMID: 26139213 DOI: 10.1152/japplphysiol.00127.2015] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2015] [Accepted: 06/28/2015] [Indexed: 11/22/2022] Open
Abstract
Lower body negative pressure (LBNP) is often used to simulate blood loss in humans. It is unknown if cerebral blood flow responses to actual blood loss are analogous to simulated blood loss during LBNP. Nine healthy men were studied at baseline, during three levels of LBNP (5 min at -15, -30, and -45 mmHg), and during three levels of blood loss (333, 667, and 1,000 ml). LBNP and blood loss conditions were randomized. Intra-arterial mean arterial pressure (MAP) during LBNP was similar to that during blood loss (P ≥ 0.42). Central venous pressure (2.8 ± 0.7 vs. 4.0 ± 0.8, 1.2 ± 0.6 vs. 3.5 ± 0.8, and 0.2 ± 0.9 vs. 2.1 ± 0.9 mmHg for levels 1, 2, and 3, respectively, P ≤ 0.003) and stroke volume (71 ± 4 vs. 80 ± 3, 60 ± 3 vs. 74 ± 3, and 51 ± 2 vs. 68 ± 4 ml for levels 1, 2, and 3, respectively, P ≤ 0.002) were lower during LBNP than blood loss. Despite differences in central venous pressure, middle cerebral artery velocity (MCAv) and cerebrovascular conductance were similar between LBNP and blood loss at each level (MCAv at level 3: 62 ± 6 vs. 66 ± 5 cm/s, P = 0.37; cerebrovascular conductance at level 3: 0.72 ± 0.05 vs. 0.73 ± 0.05 cm·s(-1)·mmHg(-1), P = 0.53). While the slope of the MAP-MCAv relationship was slightly different between LBNP and blood loss (0.41 ± 0.03 and 0.66 ± 0.04 cm·s(-1)·mmHg(-1), respectively, P = 0.05), time domain gain between MAP and MCAv at maximal LBNP/blood loss (P = 0.23) and low-frequency MAP-mean MCAv transfer function coherence, gain, and phase were similar (P ≥ 0.10). Our results suggest that cerebral hemodynamic responses to LBNP to -45 mmHg and blood loss up to 1,000 ml follow a similar trajectory, and the arterial pressure-cerebral blood velocity relationship is not altered from baseline under these conditions.
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Affiliation(s)
- Caroline A Rickards
- Department of Integrative Physiology and Anatomy and Cardiovascular Research Institute, University of North Texas Health Science Center, Fort Worth, Texas;
| | - Blair D Johnson
- Department of Anesthesiology, Mayo Clinic, Rochester, Minnesota
| | - Ronée E Harvey
- Department of Anesthesiology, Mayo Clinic, Rochester, Minnesota
| | | | | | - Jill N Barnes
- Department of Anesthesiology, Mayo Clinic, Rochester, Minnesota; Department of Physiology and Biomedical Engineering, Mayo Clinic, Rochester, Minnesota
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Riordan MA, Kyle M, Dedeo C, Villwock MR, Bauer M, Vallano ML, Deshaies EM. Mild exercise reduces cerebral vasospasm after aneurysm subarachnoid hemorrhage: a retrospective clinical study and correlation with laboratory investigation. ACTA NEUROCHIRURGICA. SUPPLEMENT 2015; 120:55-61. [PMID: 25366600 DOI: 10.1007/978-3-319-04981-6_10] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
BACKGROUND Aneurysmal subarachnoid hemorrhage (SAH) is a leading cause of death and disability and is often complicated by cerebral vasospasm (CV). Conventional management to prevent CV includes bedrest; however, inactivity places the patient at risk for nonneurological complications. We investigated the effect of mild exercise after SAH in clinical and laboratory settings. METHODS Clinical: Data from 80 patients with SAH were analyzed retrospectively. After aneurysms were secured, physical therapy was initiated as tolerated. CV and complications were compared by the timing of active physical therapy. Laboratory: 18 Rodents were divided into three groups: (1) control, (2) SAH without exercise, and (3) SAH plus mild exercise. On day 5, brainstems were removed and analyzed for the injury marker inducible nitric oxide synthase (iNOS). RESULTS Clinical: Mild exercise before day 4 significantly lowered the incidence of symptomatic CV compared with the nonexercised group. There was no difference in the incidence of additional complications based upon exercise. Laboratory: Staining for iNOS was significantly higher in the SAH group than the control group, but there was no difference between exercised and nonexercised SAH groups, confirming that exercise did not promote neuronal injury. CONCLUSION Early mobilization significantly reduced clinical CV. The relationship should be studied further in a prospective trial with defined exercise regimens.
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Affiliation(s)
- Margaret A Riordan
- Department of Neurosurgery, SUNY Upstate Medical University, Syracuse, NY, USA
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Kizilbash SJ, Ahrens SP, Bruce BK, Chelimsky G, Driscoll SW, Harbeck-Weber C, Lloyd RM, Mack KJ, Nelson DE, Ninis N, Pianosi PT, Stewart JM, Weiss KE, Fischer PR. Adolescent fatigue, POTS, and recovery: a guide for clinicians. Curr Probl Pediatr Adolesc Health Care 2014; 44:108-33. [PMID: 24819031 PMCID: PMC5819886 DOI: 10.1016/j.cppeds.2013.12.014] [Citation(s) in RCA: 82] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/08/2013] [Revised: 10/22/2013] [Accepted: 12/13/2013] [Indexed: 12/15/2022]
Abstract
Many teenagers who struggle with chronic fatigue have symptoms suggestive of autonomic dysfunction that may include lightheadedness, headaches, palpitations, nausea, and abdominal pain. Inadequate sleep habits and psychological conditions can contribute to fatigue, as can concurrent medical conditions. One type of autonomic dysfunction, postural orthostatic tachycardia syndrome, is increasingly being identified in adolescents with its constellation of fatigue, orthostatic intolerance, and excessive postural tachycardia (more than 40 beats/min). A family-based approach to care with support from a multidisciplinary team can diagnose, treat, educate, and encourage patients. Full recovery is possible with multi-faceted treatment. The daily treatment plan should consist of increased fluid and salt intake, aerobic exercise, and regular sleep and meal schedules; some medications can be helpful. Psychological support is critical and often includes biobehavioral strategies and cognitive-behavioral therapy to help with symptom management. More intensive recovery plans can be implemented when necessary.
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Affiliation(s)
- Sarah J Kizilbash
- Department of Pediatric and Adolescent Medicine, Mayo Clinic, Rochester, MN
| | - Shelley P Ahrens
- Department of Pediatric and Adolescent Medicine, Mayo Clinic, Rochester, MN
| | - Barbara K Bruce
- Department of Pediatric and Adolescent Medicine, Mayo Clinic, Rochester, MN
| | - Gisela Chelimsky
- Department of Pediatric and Adolescent Medicine, Mayo Clinic, Rochester, MN
| | | | | | - Robin M Lloyd
- Department of Pediatric and Adolescent Medicine, Mayo Clinic, Rochester, MN
| | - Kenneth J Mack
- Department of Pediatric and Adolescent Medicine, Mayo Clinic, Rochester, MN
| | - Dawn E Nelson
- Department of Pediatric and Adolescent Medicine, Mayo Clinic, Rochester, MN
| | - Nelly Ninis
- Department of Pediatric and Adolescent Medicine, Mayo Clinic, Rochester, MN
| | - Paolo T Pianosi
- Department of Pediatric and Adolescent Medicine, Mayo Clinic, Rochester, MN
| | - Julian M Stewart
- Department of Pediatric and Adolescent Medicine, Mayo Clinic, Rochester, MN
| | - Karen E Weiss
- Department of Pediatric and Adolescent Medicine, Mayo Clinic, Rochester, MN
| | - Philip R Fischer
- Department of Pediatric and Adolescent Medicine, Mayo Clinic, Rochester, MN
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Jeong SM, Hwang GS, Kim SO, Levine BD, Zhang R. Dynamic cerebral autoregulation after bed rest: effects of volume loading and exercise countermeasures. J Appl Physiol (1985) 2014; 116:24-31. [DOI: 10.1152/japplphysiol.00710.2013] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
This study assessed effects of head-down-tilt (HDT) bed rest on dynamic cerebral autoregulation (CA) in 21 healthy young adults with volume loading and exercise countermeasures. Of these, seven underwent an 18-day bed rest without exercise countermeasures ( sedentary group). Volume loading with dextran infusion was performed after bed rest to restore reduced plasma volume to levels before bed rest. In the other 14 subjects, supine cycling during bed rest was performed to preserve cardiac work from before bed rest ( exercise group). Volume loading was also performed in a subgroup of these subjects ( Ex+Dex, n = 7). Dynamic CA was estimated by transfer function analysis of changes in arterial pressure and cerebral blood flow (CBF) velocity in the very low (VLF, 0.02–0.07 Hz), low (LF, 0.07–0.20 Hz), and high frequency ranges (HF, 0.20–0.35 Hz). After bed rest, transfer function gain was reduced in the sedentary group (VLF, 0.93 ± 0.23 to 0.61 ± 0.23 cm−1·s−1·mmHg; P = 0.007) and in the exercise group (LF, 1.22 ± 0.43 to 0.94 ± 0.26 cm−1·s−1·mmHg; P = 0.005, HF, 1.32 ± 0.55 to 1.00 ± 0.32 cm−1·s−1·mmHg; P = 0.010). After volume loading, transfer function gain increased in the sedentary group but not in the Ex+Dex group. Taken together, these findings suggest that dynamic CA was preserved or improved after HDT bed rest in both sedentary and exercise subjects. Furthermore, increases of transfer function gain with volume loading suggest that changes in plasma volume may play an important role in CBF regulation.
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Affiliation(s)
- Sung-Moon Jeong
- Institute for Exercise and Environmental Medicine, Presbyterian Hospital of Dallas and University of Texas Southwestern Medical Center at Dallas, Dallas, Texas
- Department of Anesthesiology and Pain Medicine, College of Medicine, University of Ulsan, Asan Medical Center, Seoul, Korea; and
| | - Gyu-Sam Hwang
- Department of Anesthesiology and Pain Medicine, College of Medicine, University of Ulsan, Asan Medical Center, Seoul, Korea; and
| | - Seon-Ok Kim
- Department of Clinical Epidemiology and Biostatistics, College of Medicine, University of Ulsan, Asan Medical Center, Seoul, Korea
| | - Benjamin D. Levine
- Institute for Exercise and Environmental Medicine, Presbyterian Hospital of Dallas and University of Texas Southwestern Medical Center at Dallas, Dallas, Texas
| | - Rong Zhang
- Institute for Exercise and Environmental Medicine, Presbyterian Hospital of Dallas and University of Texas Southwestern Medical Center at Dallas, Dallas, Texas
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Lucas RAI, Pearson J, Schlader ZJ, Crandall CG. Hypercapnia-induced increases in cerebral blood flow do not improve lower body negative pressure tolerance during hyperthermia. Am J Physiol Regul Integr Comp Physiol 2013; 305:R604-9. [PMID: 23864641 DOI: 10.1152/ajpregu.00052.2013] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Heat-related decreases in cerebral perfusion are partly the result of ventilatory-related reductions in arterial CO2 tension. Cerebral perfusion likely contributes to an individual's tolerance to a challenge like lower body negative pressure (LBNP). Thus increasing cerebral perfusion may prolong LBNP tolerance. This study tested the hypothesis that a hypercapnia-induced increase in cerebral perfusion improves LBNP tolerance in hyperthermic individuals. Eleven individuals (31 ± 7 yr; 75 ± 12 kg) underwent passive heat stress (increased intestinal temperature ∼1.3°C) followed by a progressive LBNP challenge to tolerance on two separate days (randomized). From 30 mmHg LBNP, subjects inhaled either (blinded) a hypercapnic gas mixture (5% CO2, 21% oxygen, balanced nitrogen) or room air (SHAM). LBNP tolerance was quantified via the cumulative stress index (CSI). Mean middle cerebral artery blood velocity (MCAvmean,) and end-tidal CO2 (PetCO2) were also measured. CO2 inhalation of 5% increased PetCO2 at ∼40 mmHg LBNP (by 16 ± 4 mmHg) and at LBNP tolerance (by 18 ± 5 mmHg) compared with SHAM (P < 0.01). Subsequently, MCAvmean was higher in the 5% CO2 trial during ∼40 mmHg LBNP (by 21 ± 12 cm/s, ∼31%) and at LBNP tolerance (by 18 ± 10 cm/s, ∼25%) relative to the SHAM (P < 0.01). However, hypercapnia-induced increases in MCAvmean did not alter LBNP tolerance (5% CO2 CSI: 339 ± 155 mmHg × min; SHAM CSI: 273 ± 158 mmHg × min; P = 0.26). These data indicate that inhaling a hypercapnic gas mixture increases cerebral perfusion during LBNP but does not improve LBNP tolerance when hyperthermic.
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Affiliation(s)
- Rebekah A I Lucas
- Institute for Exercise and Environmental Medicine, Texas Health Presbyterian Hospital, Dallas, Texas and Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas
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Perry BG, Schlader ZJ, Raman A, Cochrane DJ, Lucas SJE, Mündel T. Middle cerebral artery blood flow velocity in response to lower body positive pressure. Clin Physiol Funct Imaging 2013; 33:483-8. [PMID: 23701382 DOI: 10.1111/cpf.12046] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2013] [Accepted: 04/09/2013] [Indexed: 11/28/2022]
Abstract
Lower body positive pressure (LBPP) has been used in the treatment of haemorrhagic shock and in offsetting g-force induced fluid shifts. However, the middle cerebral artery blood flow velocity (MCAv) response to supine LBPP is unknown. Fifteen healthy volunteers (mean ± SD: age, 26 ± 5 year; body mass, 79 ± 10 kg; height, 174 ± 9 cm) completed 5 minutes of 20 and 40 mm Hg LBPP, in a randomized order, separated by 5 minutes rest (baseline). Beat-to-beat MCAv and blood pressure, partial pressure of end-tidal carbon dioxide (PET CO2 ) and heart rate were recorded and presented as the change from the preceding baseline. All measures were similar between baseline periods (all P>0·30). Mean arterial pressure (MAP) increased by 7 ± 6 (8 ± 7%) and 13 ± 7 mm Hg (19 ± 11%) from baseline during 20 and 40 mm Hg (P<0·01), respectively. The greater MAP increase at 40 mm Hg (P<0·01 versus 20 mm Hg) was mediated via a greater increase in total peripheral resistance (P<0·01), with heart rate, cardiac output (Model flow) and PET CO2 remaining unchanged (all P>0·05) throughout. MCAv increased from baseline by 3 ± 4 cm s(-1) (5 ± 5%) during 20 mm Hg (P = 0·003), whilst no change (P = 0·18) was observed during 40 mm Hg. Our results indicate a divergent response, in that 20 mm Hg LBPP-induced modest increases in both MCAv and MAP, yet no change in MCAv was observed at the higher LBPP of 40 mm Hg despite a further increase in MAP.
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Affiliation(s)
- Blake G Perry
- School of Sport and Exercise, Massey University, Palmerston North, New Zealand
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